Fireproof heat insulating barrier, method for making same, garmet comprising at least such a barrier as internal insulation

ABSTRACT

A fireproof thermally insulating barrier ( 1 ) for a safety garment, the barrier comprising a front face for facing an external source of heat or radiation, and a rear face opposite from its front face, the barrier being characterized in that it includes a plurality of perforations ( 2, 3 ) each opening out to the front face and to the rear face of said barrier ( 1 ). A method of manufacturing such a barrier and a fireproof safety garment comprising at least one such barrier as internal thermal insulation.

[0001] The invention relates to the technical field of textile materialsthat are thermally insulating and fireproof.

[0002] The term “thermally insulating” is used herein to mean textilematerials through which heat flux densities are low when the materialsare subjected to a temperature gradient.

[0003] The term “fireproof” is used herein to designate textilematerials that are temperature stable, conserving good mechanicalproperties up to temperatures such as those that result from exposure to400° C.

[0004] The invention relates particularly, but not exclusively, tothermally insulating linings for fireproof safety garments.

[0005] Numerous vocational activities involve a risk of being burntdirectly by a flame, by an electric arc, or by splashes of hot material,or of being burned indirectly by thermal flash.

[0006] Amongst such activities, mention should naturally be made notonly of firefighters and operators in pyrometallurgy, but also of theactivities of the armed forces, police, airplane pilots, racing cardrivers, and many others in the fields of chemistry, steel working,glassmaking, the aluminum industry, power generation, or transport, forexample.

[0007] The garment linings used in these various contexts of activitymust not only present good properties in terms of constituting a thermalbarrier and withstanding temperature, but they must also present aslittle an impact as possible on the comfort of the wearer of thegarment.

[0008] A safety garment that is uncomfortable runs the risk of notalways being worn, and a feeling of discomfort can distract attention.

[0009] Ideally, the presence of a lining should not give rise to thegarment being excessively heavy or bulky.

[0010] Also ideally, the presence of the lining should not interferewith the movements of a person nor with the evaporation of sweat.

[0011] The problem of disposing of sweat is particularly troublesomegiven that certain professional activities, such as those offirefighters when fighting a fire, need to be performed in a context ofintense physical effort and stress and in geographical areas where theclimate is already hot.

[0012] This problem is further complicated by the fact that sweatingdoes not occur in uniform manner over the entire surface of the body.

[0013] This problem is particularly serious when accumulated sweat in agarment tends to increase its thermal conductivity, thereby reducing itscapacity as an insulating barrier.

[0014] The thermal barrier properties of the lining must notsimultaneously eliminate all physical sensation of heat, since thatsensation is essential.

[0015] In particular, the presence of the fireproof insulating liningmust guarantee that the length of time between reaching the painthreshold and reaching the threshold of irreversible damage is alwaysgreater than the reaction time of a person wearing the fireproofgarment.

[0016] Conventionally, fireproof thermally insulating linings are madeof material that is fibrous and porous.

[0017] The use of fibrous and porous materials for making such liningsis justified by their heat transfer properties.

[0018] This transfer takes place by radiation, by conduction, and bynatural convection.

[0019] Radiation is the mode of transfer which is usually dominant infibrous materials, particularly when the temperature gradient to whichthey are exposed is large.

[0020] The conduction flux density depends on the overall porosity ofthe fiber material, on the area per unit volume of the fibers which isrepresentative of the extent to which the fibers are divided, and on theanisotropy with which the fibers are distributed.

[0021] In general, the natural convection flux density is limited inthermally insulating fiber materials.

[0022] The insulation obtained by a sheet of fibrous material isgenerally inversely proportional to the density of the material, to thedensity of the fibers making it up, and to the thermal conductivity ofthese components. This insulation is proportional to the thickness ofthe sheet.

[0023] The items described above show that fireproof insulating liningsneed to satisfy requirements that are varied and sometimescontradictory.

[0024] Three examples of such contradictions can be given.

[0025] A first example is associated with choosing a value for theporosity of the lining material.

[0026] Maximum porosity can be desired for the fibrous and porousmaterial of the lining. The air between the fibers is a medium which isentirely transparent to radiation so only the fibers are involved indiffusing, absorbing, and re-emitting infrared radiation. Howevermaximum porosity can give rise to poor mechanical behavior, inparticular during washing and while a garment is being worn, or it canlead to the volume of the lining being excessive, thus impeding themovements of the wearer of the garment.

[0027] A second example is associated with selecting a thickness for thelining material.

[0028] A thick lining does indeed have a high level of insulating power,particularly with decreasing volume of fiber used per unit volume of thelining. However, a thick lining can impede the movements of the wearerof the garment. In addition, the lining must not be made highlythermally insulating to the detriment of a physical sensation of pain,where the pain threshold varies from one person to another.

[0029] A third example is more fundamentally associated with selecting alining that is highly thermally insulating. Conventionally, putting athermal barrier into place against temperature gradients going from theoutside of the garment towards the inside of the garment automaticallyleads also to creating a thermal barrier against temperature gradientsgoing from the inside of the garment towards the outside thereof. Thiscan lead to a sensation of discomfort, particularly in hot or desertclimates, since removal of sweat and body heat is prevented by thepresence of the lining.

[0030] The need to remove heat and sweat becomes even more necessarywhen fireproof safety garments are thick and sometimes heavy.

[0031] Conventionally, fireproof safety garments comprise, from theirouter face towards their inner face:

[0032] an outer cloth, usually based on aramid, usually having a massper unit area of 200 grams per square meter (g/m³) to 250 g/m³;

[0033] a breathing waterproof microporous membrane of the PTFE orphosphorous-containing polyurethane, assembled on a substrate, usuallyof aramid fibers, or assembled on another layer;

[0034] a thermally insulating barrier, usually formed by a non-wovenfabric of aramid fibers; and

[0035] a cleanliness lining, usually comprising 100% aramid or 50%aramid and 50% fire resistant (FR) viscose, protecting the thermalbarrier.

[0036] Various embodiments of thermally insulating and fireproofbarriers have been proposed in the prior art.

[0037] Conventionally, those thermal barriers implement non-wovenfabric, woven fabrics, or knits that are thermally stable andnon-flammable because of the nature of the fibers used.

[0038] The thermal barriers known in the prior art satisfy the needs oftheir users only partially, in particular concerning their capacity forheat exchange from their inside faces towards their outside faces.

[0039] An object of the invention is to propose a fireproof,thermostable, thermally insulating barrier, enabling increased amountsof heat and body sweat to be removed, so as to maintain an impression ofa second skin for a person using a garment provided with such a thermalbarrier, the barrier nevertheless retaining good properties ofprotection against fire and against thermal flashes.

[0040] To this end, in a first aspect, the invention provides afireproof and thermostable thermally insulating barrier, in particularfor a safety garment, the barrier having a front face for facing anexternal source of heat or radiation, and a rear face opposite from itsfront face, said sheet including a plurality of holes each opening outto the front face and to the rear face of said sheet.

[0041] The size, the shape, and the density of the holes are such thatthe natural heat of the human body can be removed more easily, whilenevertheless maintaining the thermal barrier effect for sources of heatthat are external.

[0042] In various embodiments, the sheet is made from a polymer materialselected from the group comprising: polyamide imides polyimides (PI)such as P.84, aramids, para-aramids, meta-aramids, polyacrylates,aromatic copolyimides, polyacrylonitriles, polyester-ether-ketone,polybenzimidazoles, polytetrafluorethylenes (PTFE), polysulfones (PSO),polyethersulfones (PES), polyphenylsulfones, and phenylene polysulfides(PPS), mixtures of aramid and polybenzimidazole, thermally stabilizedmixtures of polyacrylonitrile and polyamide, polytrifluorochlorethylenes(PTFCE), copolymers of tetrafluoroethene and perfluoroprene (FEP),melamines (e.g. Basofil®) and phenolic polymers (e.g. Kynol®)

[0043] In certain embodiments, the thermal barrier is made from fibersof the above-mentioned polymer materials, or from mixtures of fibers ofat least two of said polymer materials.

[0044] In particular embodiments, this thermal barrier is made of acomposite material provided with a matrix based on a polymer materialselected from those mentioned above and reinforcement based on short orlong fibers, which can be woven or non-woven.

[0045] In various embodiments, these reinforcing fibers are selectedfrom the group comprising metal fibers, glass fibers, “non-fire” viscosefibers, carbon fibers, peroxidized carbon fibers, modacrylic fibers.

[0046] In a low-cost embodiment, the thermal barrier is made as acomposite material reinforced with recycled aramid fibers.

[0047] In a second aspect, the invention provides a method ofmanufacturing a sheet of the kind presented above, the method includinga needling step.

[0048] In a third aspect, the invention provides a fireproof protectivegarment, comprising at least one fireproof thermostable thermal barrieras described above.

[0049] In certain embodiments, the garment further comprises, going fromits outside face towards its inside face: an aramid-based fabric, abreathing waterproof microporous membrane, said fireproof thermostablethermal barrier, and a cleanliness lining.

[0050] By way of example, the semipermeable membrane is made from asheet of phosphorous-containing polyurethane or PTFE, assembled on anaramid fiber substrate.

[0051] Other objects and advantages of the invention appear from thefollowing description of embodiments, which description is made withreference to the accompanying drawing, in which:

[0052]FIG. 1 is a front view of a portion of a fireproof thermostablethermal barrier constituting an embodiment of the invention; and

[0053]FIG. 2 is a section view through a fireproof garment including athermal barrier as shown in FIG. 1.

[0054] Reference is made initially to FIG. 1, showing an embodiment ofthe invention.

[0055] In this embodiment, a needled non-woven fabric 1 that providesthermal insulation and fireproofing for insulating a safety garment isprovided with perforations 2, 3.

[0056] This needled non-woven fabric is made from mixtures of aramidfibers such as Nomex®, Isomex®, or Kevlar® from Dupont de Nemours, orKermel® from Rhone Poulenc, Teijin Conex® or Technora® fibers fromTeijin Ltd., Twaron® from Akzo, Apyeil® from Unitika, or HMA® fromHoechst.

[0057] The table below lists some of the properties of thenon-perforated non-woven fabric made from an Isomex® 5119WSM913 felt,said felt comprising a mixture of meta-aramid fibers and para-aramidfibers, of denier 1.4/1.7/2.2/6.1 dtex and of length lying in the range38 millimeters (mm) to 140 mm. Characteristics Test standard ValueTolerance Weight ISO 9073-1  155 g/m² ±8% Thickness under a ISO 9073-2 2.5 mm ±0.50 load of 0.5 kPa Breaking strength in ISO 9073-3 tractionWidthwise 290 N >200 Lengthwise 290 N >200 Breaking elongation ISO9073-3 in traction Widthwise 80% >100 Lengthwise 55% >80

[0058] Other thermostable synthetic fibers can be used, such as thefollowing:

[0059] melamine fibers, e.g. Basofil®;

[0060] aromatic polyamide fibers, e.g. P84® from Lenzing;

[0061] phenolic fibers, e.g. Kynol® from Nippon Kynol or Philene® fromSaint Gobain;

[0062] pan preox fibers, e.g. Panox® from RK Carbon Ltd., or Sigrafil®from Sigri;

[0063] polyacrylate fibers, e.g. Inidex® from Courtaulds; and

[0064] polybenzimidazole fibers, e.g. PBI® from Hoechest Celanese.

[0065] In most applications, a suitable weight for the non-woven feltlies in the range 100 g/m² to 200 g/m².

[0066] The aramid fibers used can be derived from recycling, e.g. scrap.

[0067] In the embodiment shown, the perforations made through theneedled non-woven sheet are circular holes 2, 3 of two differentdiameters.

[0068] In FIG. 1, in order to make the description easier to understand,directions D1 and D2 are defined as the longitudinal and transversedirections respectively.

[0069] The terms “longitudinal” and “transverse” are used forconvenience and do not determine the orientation of the sheet in use.

[0070] In the embodiment shown, a first type of hole 2 has a diameter ofabout 3 millimeters while a second type of hole 3 has a diameter ofabout 2 millimeters.

[0071] The larger diameter holes 2 are disposed in a rectangular meshpattern.

[0072] The smaller diameter holes 3 are disposed in the same rectangularmesh pattern, with the two patterns being offset by half a mesh size.

[0073] As a result, the smaller diameter holes are disposed inequidistant longitudinal lines that are spaced apart identically to thespacing of the larger diameter holes.

[0074] Similarly, the larger diameter holes are disposed in equidistanttransverse lines that are spaced apart identically to the spacingbetween the smaller diameter holes.

[0075] When seen along two directions D3, D4 that are oblique relativeto the directions D1, D2, the holes 2, 3 are in lines.

[0076] The four neighboring holes closest to each smaller diameter hole3 are larger diameter holes 2 disposed in the mesh of their array.

[0077] Similarly, the four neighboring holes closest to each largerdiameter hole 2 are smaller diameter holes 3, disposed in the mesh oftheir array.

[0078] The density of the holes is of the order of two to three holesper square centimeter.

[0079] Perforation enables the weight of the sheet to be reduced byabout 20% to 30%.

[0080] Other forms of hole could be envisaged, as could other patternsof holes.

[0081] The thermal barrier can also have more than two types of hole.

[0082] In certain embodiments, perforation density is not uniform.

[0083] Thus, when the thermal barrier 1 is installed as insulation in afireproof garment, a greater density of holes can be provided for thoseregions of the body that, a priori, are relatively little exposed to therisk of being burnt directly or indirectly.

[0084] Similarly, if the thermal barrier 1 is used as insulation in afireproof protective hood, then the perforations can be more numerousover the ears of the wearer of the hood.

[0085] In the embodiment shown, the perforations are disposed in apattern that is simple and regular.

[0086] Amongst other advantages, this type of embodiment presents theadvantage of making it easier to model the thermal and mechanicalbehavior of the fireproof insulating thermostable thermal barrier.

[0087] Naturally, irregular patterns can be envisaged, depending onrequirements.

[0088] The fireproof insulating thermostable thermal barrier made ofneedled non-woven fabric is flexible, being about one to fivemillimeters thick, for example.

[0089] Reference is now made to FIG. 2.

[0090]FIG. 2 is a diagrammatic cross-section through the structure of aprotective garment comprising at least one thermal barrier 1 as internalinsulation.

[0091] For reasons of clarity, the various garment layers are shown asbeing spaced apart from one another in FIG. 2.

[0092] The relative thickness of the various layers are not exact, andthe thickness of the lining has been exaggerated for reasons of clarity.

[0093] Going from its outside face towards its inside face, thefireproof safety garment comprises:

[0094] an outer cloth 4;

[0095] a microporous membrane 5;

[0096] said fireproof thermostable thermal barrier; and

[0097] an inner cleanliness lining 6.

[0098] The resistance to evaporation of garments of the above type, whenprovided with a conventional lining, generally lies in the range 22 barsquare meters per watt (bar.m²/W) to 30 bar.m²/W.

[0099] Such values are obtained, for example, when using a needlednon-woven fabric of Isomex® fibers weighing 100 g/m².

[0100] The use of Nomex® type fibers makes it possible to reduce thisvalue of resistance to evaporation to below 22 bar.m²/W.

[0101] Making perforations through an Isomex® needled non-woven fabricenables the value of resistance to evaporation to be improved by 10% to30%.

[0102] In certain embodiments, the outer cloth 4 is substantiallywaterproof.

[0103] This property is particularly important for certain actions takenby firefighters or when the atmosphere in which action is being taken ispotentially harmful or toxic.

[0104] In certain embodiments, the outer cloth is provided withphosphorescent and/or fluorescent strips.

[0105] By way of example, the microporous membrane 5 is made ofGore-tex® or is of the phosphorous-containing polyurethane typeassembled on a substrate of aramid fibers.

[0106] Depending on the expected exposure temperatures, various types offiber can be used for making a non-woven thermal barrier 1.

[0107] For exposure to high temperatures, it is possible to use fibersof the following types:

[0108] polyamide imides, polyimides (PI);

[0109] aramids such as Kermel®, Teijin Conex®, Kevlar®, Twaron®,Tecnora®;

[0110] para-aramids, meta-aramids;

[0111] polyacrylate such as Inidex®;

[0112] aromatic copolyimide;

[0113] polyacrylonitrile;

[0114] polyester-ether-ketone;

[0115] polybenzimidazole, e.g. PBI® fibers from Celanise Corp.;

[0116] polytetrafluorethylene (PTFE);

[0117] modacrylics;

[0118] polyphenylsulfone; and

[0119] phenylene polysulfide (PPS).

[0120] It is also possible to use mixtures of fibers of the above type,and in particular:

[0121] a mixture of aramid and of polybenzimidazole;

[0122] thermally stabilized mixtures of polyacrylonitrile and polyamide.

[0123] Where appropriate, the above-mentioned fibers, and in particularpolyaramids, can be mixed with glass fibers, carbon fibers, or silicafibers.

[0124] When exposure to lower temperatures is expected, it is possibleto fibers of the following types:

[0125] polytrifluorochlorethylene (PTFCE);

[0126] a copolymer of tetrafluoroethene and perfluoroprene (i.e.fluorinated-ethlene-propylene (FEP));

[0127] polysulfone (PSO); and

[0128] polyethersulfone (PES).

[0129] When mechanical strength and the ability to withstand washing aremore particularly desired for the perforated needled non-woven felts, itcan be sewn to a fireproof membrane, using lines of stitches that arenot rectilinear but that are sinuous, for example.

1/ A fireproof and thermostable thermally insulating barrier, inparticular for a safety garment, the barrier having a front face forfacing an external source of heat or radiation, and a rear face oppositefrom its front face, and being characterized in that it includes aplurality of holes (2, 3) each opening out to the front face and to therear face of said sheet. 2/ An insulating barrier according to claim 1,characterized in that the density of holes is about two per squarecentimeter. 3/ An insulating barrier according to claim 1 or claim 2,characterized in that the holes are circular. 4/ An insulating barrieraccording to claim 3, characterized in that the holes are of two types,each type of hole having a diameter that is different from the diameterof the other type of hole. 5/ An insulating barrier according to claim4, characterized in that the first type of hole (2) has a diameter ofabout three millimeters. 6/ An insulating barrier according to claim 4or claim 5, characterized in that the second type of hole (3) has adiameter of about two millimeters. 7/ An insulating barrier according toany one of claims 4 to 6, characterized in that each of the two types ofhole (2, 3) is disposed in a rectangular mesh pattern. 8/ An insulatingbarrier according to claim 7, characterized in that the two rectangularpatterns are identical and offset. 9/ An insulating barrier according toclaim 8, characterized in that the two patterns are offset by half themesh size. 10/ An insulating barrier according to any one of claims 1 to9, characterized in that its thickness is about five millimeters. 11/ Aninsulating barrier according to any one of claims 1 to 10, characterizedin that it is made from a material selected from the group comprising:polyamide imides , polyimides (PI), aramids, para-aramids, meta-aramids,polyacrylates, aromatic copolyimides, polyacrylonitriles,polyester-ether-ketone, polybenzimidazole, polytetrafluorethylene(PTFE), polysulfones (PSO), polyethersulfones (PES), polyphenylsulfones,and phenylene polysulfides (PPS), mixtures of aramid andpolybenzimidazole, thermally stabilized mixtures of polyacrylonitrileand polyamide, polytrifluorochlorethylenes (PTFCE), copolymers oftetrafluoroethene and perfluoroprene (FEP). 12/ An insulating barrieraccording to claim 11, characterized in that it is made from a materialfurther comprising fibers selected from the group comprising: metalfibers, glass fibers, “non-fire” viscose fibers, carbon fibers,peroxided carbon fibers, silica fibers, modacrylic fibers. 13/ Aninsulating barrier according to any one of claims 1 to 12, characterizedin that it is in the form of a non-woven fabric. 14/ An insulatingbarrier according to claim 13, characterized in that it is made fromrecycled aramid fibers. 15/ A method of manufacturing an insulatingbarrier as presented in claim 13 or claim 14, characterized in that themethod includes a needling step. 16/ A fireproof protective garment,characterized in that it comprises at least one thermally insulatingbarrier (1) as presented in any one of claims 1 to 13 as internalinsulation. 17/ A garment according to claim 16, characterized in thatit comprises: an aramid-based outer cloth (3); a breathing waterproofmicroporous membrane (4); said thermally insulating barrier (5); and aninternal cleanliness lining (6). 18/ A garment according to claim 16 or17, characterized in that the microporous membrane (4) is made from asheet of phosphorous-containing polyurethane, assembled to a substrateof aramid fibers.